Motor vehicle headlight with high-pressure gas discharge lamp

ABSTRACT

An automotive headlight with a high-pressure gas discharge lamp ( 6 ) arranged inside a reflector contains an electronic ballast ( 8 ) in a housing for operation of the high-pressure gas discharge lamp. The housing ( 1 ) is designed to dissipate heat and provide electromagnetic shielding, so as to dissipate the heat generated by the electronic unit ( 8 ) in particular and possibly also by the high-pressure gas discharge lamp ( 6 ) and to provide a shield against the resulting electronic radiation. Cooling ribs ( 11 ) may be provided on the housing ( 1 ). The invention makes available an electromagnetically compatible ballast for high-pressure gas discharge lamps.

BACKGROUND OF THE INVENTION

[0001] The invention relates to an automotive headlight with ahigh-pressure gas discharge lamp of the generic type defined in thepreamble of claim 1.

[0002] With a known automotive headlight with a high-pressure gasdischarge lamp of this type (German Patent No. 35 19 611 A1), a moldedhousing is provided on the rear part of the reflector. The housingcontains an electronic ballast that supplies the lamp with a highfrequency starting and operating voltage. The high-pressure gasdischarge lamp is inserted directly into the ballast through an openingin the reflector. An elastic sealing compound is inserted between thereflector and the molded housing to protect against harmful effects ofmoisture and corrosion. The ballast is supplied with voltage from thevehicle's on-board electric system over a simple pair of cables.

[0003] With this known automotive headlight with a high-pressure gasdischarge lamp, the molded housing is described explicitly as made ofplastic. Together with the installation site directly on the reflector,this serves to design and arrange the ballast in the motor vehicle sothat it is protected from the effects of weather without requiring anyadditional space; electric sparkover to other parts of the vehicle beingprevented and the high-voltage lines being short to reduce capacitivelosses.

[0004] This plastic housing for the ballast is not capable ofdissipating enough of the heat generated in its interior by the lamp andits electronic unit. In addition, this plastic housing is unable toprevent interference voltage generated in its interior by the electronicunit of the ballast from being radiated out of the housing. Electroniccomponents and devices in the engine compartment are thus endangered bythe interference voltage emitted. Therefore, the requiredelectromagnetic compatibility of this known arrangement is notguaranteed.

ADVANTAGES OF THE INVENTION

[0005] The automotive headlight according to this invention with ahigh-pressure gas discharge lamp having the characterizing features ofclaim 1, has the advantage over the related art of guaranteeddissipation of heat to protect the electronic unit accommodated in theinterior of the housing, plus total shielding of the interior of thehousing from the environment so that ballast-generated interferencevoltage is not radiated out of the housing. The electromagneticcompatibility of the automotive headlight with a high-pressure gasdischarge lamp designed according to this invention is thus ensured.This is an extremely important prerequisite for practical use. The partscontained in the interior of the housing are thus of course alsoprotected and shielded from effects from the external environment bythis advantageous embodiment. This also increases their functionalreliability.

[0006] According to this invention, the housing is designed to dissipateheat and provide electromagnetic shielding to dissipate the heatgenerated by the electronic unit and possibly also the high-pressure gasdischarge lamp and to provide a shield against the resultingelectromagnetic radiation.

[0007] Advantageous refinements and improvements on the automotiveheadlight characterized in claim 1 are possible through the measuresspecified in the additional claims.

[0008] According to an especially advantageous embodiment of theinvention, the housing is provided with an internal and/or externalcoating to provide a shield against electromagnetic radiation from theelectronic unit or the environment.

[0009] In an advantageous alternative embodiment, the material providedfor the housing may be one that not only dissipates heat but alsofulfills the function of providing electromagnetic shielding.

[0010] For more reliable and more intense dissipation of heat, thehousing according to an expedient refinement of the invention isprovided with parts that enlarge the surface area, in particular in theform of cooling ribs, for the purpose of dissipation of heat.

[0011] In another advantageous embodiment of the invention, thehigh-pressure gas discharge lamp is either permanently or replaceablyattached to the housing.

[0012] To make handling of installation simple and acceptable, thehousing may be attached to the reflector by means of a standardizedlocking mechanism, in particular a bayonet lock, in an advantageousembodiment of the invention.

DRAWING

[0013] The invention is explained in greater detail in the followingdescription on the basis of an embodiment illustrated in the FIGURE,which shows:

[0014]FIG. 1 a perspective schematic view of a housing designedaccording to this invention, with a corner cut away to provide a viewinto the interior.

DESCRIPTION OF THE EMBODIMENT

[0015]FIG. 1 shows a schematic perspective view of a housing 1 designedaccording to this invention, with one corner 3 cut away to allow a viewinto interior 2. A cover 4 of housing 1 is shown slightly lifted away tobetter illustrate a base 5 for a high-pressure gas discharge lamp 6.Base 5 contains two terminal posts 7 into which terminal electrodes(inside socket 5, but not shown here) of the high-pressure gas dischargelamp 6 can be inserted. High-pressure gas discharge lamp 6 is suppliedvia terminal posts 7 with electric power generated by electronic unit 8(only suggested in the figure) and is thereby controlled and regulated.Electronic unit 8 itself is supplied with d.c. voltage of 12 V, forexample, from the automotive battery (not shown) over simple cable sets9 and 10 which are led into housing 1 at a suitable location.

[0016] According to this invention, housing 1 is designed to dissipateheat and provide electromagnetic shielding. Thus, the heat is removed,in particular the heat generated by electronic unit 8 and possibly alsoby high-pressure gas discharge lamp 6, and the shielding is providedagainst the resulting electromagnetic radiation. According to anespecially advantageous embodiment of the invention, housing 1 is madeof a heat-dissipating material. In another advantageous embodiment,housing 1 may be provided with a coating inside and/or outside toprovide a shield against the electromagnetic radiation of electronicunit 8 or radiation coming from the outside.

[0017] In an advantageous alternative embodiment, the material providedfor housing 1 may be one that not only dissipates heat but also fulfillsthe function of providing electromagnetic shielding.

[0018] For more reliable and more intense dissipation of heat, housing 1is provided with parts that increase the surface area to dissipate heat,in particular in the form of cooling ribs 11.

[0019] In another advantageous embodiment of the invention,high-pressure gas discharge lamp 6 is either permanently or replaceablyattached to housing 1. In the embodiment according to FIG. 1, base 5with high-pressure gas discharge lamp 6 is designed to be removable.

[0020] To make installation simple and acceptable, in an advantageousembodiment of the invention, housing 1 can be attached to the reflectorby means of a standardized locking mechanism, in particular a bayonetlock. Neither this bayonet lock nor the reflector is shown in theembodiment illustrated in FIG. 1.

[0021] The invention makes available an electromagnetically compatibleballast for high-pressure gas discharge lamps in a very advantageousmanner.

1. Automotive headlight having a high-pressure gas discharge lamp (6)which is arranged within a reflector, comprising an electronic ballast(8) for operation of the high-pressure gas discharge lamp (6,) andcomprising a housing (1) to accommodate the electronic unit (8), thehousing (1) being arranged directly on the reflector, characterized inthat the housing (1) is designed to dissipate heat and provide anelectromagnetic shield to dissipate the heat generated by the electronicunit (8) in particular and possibly also by the high-pressure gasdischarge lamp (6) and to provide a shield against the resultingelectromagnetic radiation.
 2. Automotive headlight according to claim 1, characterized in that the housing (1) is made of a heat-dissipatingmaterial.
 3. Automotive headlight according to claim 2 , characterizedin that the housing (1) is provided with a coating on the inside and/oroutside to shield the environment or the electromagnetic radiation ofthe electronic unit (8).
 4. Automotive headlight according to claim 2 ,characterized in that the material used for the housing (1) is one thatfulfills the function of providing an electromagnetic shield in additionto dissipating heat.
 5. Automotive headlight according to one of thepreceding claims, characterized in that the housing (1) is provided withparts that enlarge the surface area, in particular in the form ofcooling ribs (11) and the like for dissipation of heat.
 6. Automotiveheadlight according to one of the preceding claims, characterized inthat the high-pressure gas discharge lamp (6) is either permanently orreplaceably attached to the housing (1).
 7. Automotive headlightaccording to one of the preceding claims, characterized in that thehousing (1) can be attached to the reflector by means of a standardizedlocking mechanism, in particular a bayonet lock.